Pex crimping tool

ABSTRACT

A power tool includes an outer housing having a drive unit support portion and a handle portion, an inner housing positioned at least partially within the outer housing, and a drive unit positioned in the drive unit support portion, the drive unit including an output member. The power tool also includes a power screw mechanism with a nut fixed relative to the outer housing and a screw coupled for co-rotation with the output member and axially movable relative to the output member. The screw is in threaded engagement with the nut such that the screw moves axially in response to rotation of the screw relative to the nut. The power tool also includes a working assembly coupled to the inner housing for movement in response to axial movement of the screw.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 15/723,647, filed Oct. 3, 2017, which is a continuation of U.S.patent application Ser. No. 15/088,199, filed Apr. 1, 2016, now U.S.Pat. No. 9,808,851, which claims priority to U.S. Provisional PatentApplication No. 62/141,957, filed Apr. 2, 2015, and U.S. ProvisionalPatent Application No. 62/192,638, filed Jul. 15, 2015, the entirecontents of all of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to power tools, and more particularly toPEX (cross-linked polyethylene) crimping tools.

BACKGROUND OF THE INVENTION

Polymer tubing is gaining popularity in residential home and commercialbuilding construction due to the rising cost of copper pipe. One of themore common types of polymer tubing is made from cross-linkedpolyethylene, commonly known as PEX. Polymer tubing is typicallyattached to fittings using compression or crimped connectors. Theseconnectors are compressed onto the PEX tubing using a crimping tool.Manual crimping tools, typically including a pair of handles foractuating a pair of crimper jaws by a pivoting linkage arrangement, arewell known.

SUMMARY OF THE INVENTION

The invention provides, in one aspect, a power tool including an outerhousing having a drive unit support portion and a handle portion, aninner housing positioned at least partially within the outer housing,and a drive unit positioned in the drive unit support portion, the driveunit including an output member. The power tool also includes a powerscrew mechanism with a nut fixed relative to the outer housing and ascrew coupled for co-rotation with the output member and axially movablerelative to the output member. The screw is in threaded engagement withthe nut such that the screw moves axially in response to rotation of thescrew relative to the nut. The power tool also includes a workingassembly coupled to the inner housing for movement in response to axialmovement of the screw.

The invention provides, in another aspect, a power tool including anouter housing having a drive unit support portion and a handle portion,an inner housing positioned at least partially within the outer housing,and a drive unit positioned in the drive unit support portion, the driveunit including an output member. The power tool also includes a rollercarriage movable between a retracted position and an extended positionin response to rotation of the output member, and a working assemblymovable in response to contact with the roller carriage. The workingassembly includes first and second jaws pivotally coupled to the innerhousing, a pin positioned between the first and second jaws and having acircumferential groove, and a biasing member at least partially receivedwithin the circumferential groove, the biasing member configured to biasthe first and second jaws toward a closed position.

The invention provides, in another aspect, a power tool including anouter housing with a drive unit support portion and a handle portion, aninner housing positioned at least partially within the outer housing,and a drive unit positioned in the drive unit support portion andincluding an output member having a plurality of internal splines. Thepower tool also includes a power screw mechanism with a nut fixedrelative to the outer housing, a screw in threaded engagement with thenut such that the screw moves axially in response to rotation of thescrew relative to the nut, and a splined member fixed to the screw, thesplined member including a plurality of external splines meshed with theinternal splines of the output member. The power tool also includes aworking assembly coupled to the inner housing for movement in responseto axial movement of the screw.

Other features and aspects of the invention will become apparent byconsideration of the following detailed description and accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a PEX crimping tool in accordance withan embodiment of the invention.

FIG. 2 is a side view of the crimping tool of FIG. 1

FIG. 3 is a perspective view of the crimping tool of FIG. 1 with aportion of an outer housing removed to show internal components of thecrimping tool.

FIG. 4 is a cross-sectional view of the crimping tool of FIG. 1 througha vertical plane passing through a longitudinal axis of the crimpingtool.

FIG. 5 is a partial cross-sectional view of the crimping tool of FIG. 1through a vertical plane passing through a longitudinal axis of thecrimping tool.

FIG. 6 is a schematic illustration of a control system used in thecrimping tool of FIG. 1.

FIG. 7 is a perspective view of a splined nut of a ball screw mechanismof another embodiment of the PEX crimping tool.

FIG. 8 is a perspective view of a pair of crimping jaws of anotherembodiment of the PEX crimping tool.

FIG. 9 is a perspective view of the crimping jaws of FIG. 8, withportions removed to expose a pivot pin and a leaf spring.

FIG. 10 is an enlarged perspective view of the pivot pin and leaf springof FIG. 9.

FIG. 11 is a perspective view of the pivot pin of FIG. 10.

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways. Also, it is to be understood thatthe phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting.

DETAILED DESCRIPTION

FIGS. 1-5 illustrate a power tool 10, which is a PEX crimping tool 10 inthe illustrated embodiment. In other embodiments, the power tool 10 maybe configured as any of a wide range of power tools (e.g., cutters,knockout punches, etc.).

The crimping tool 10 includes an outer housing 14 having a batterysupport portion 18, a drive unit support portion 26, and a handleportion 34 configured to be gripped by a user during operation of thecrimping tool 10 (FIGS. 1 and 2). With reference to FIG. 3, the batterysupport portion 18 supports a battery 22, which is a lithium-ion powertool battery pack in the illustrated embodiment, for providing power tothe crimping tool 10. Referring to FIG. 4, the drive unit supportportion 26 supports a drive unit 30, and the handle portion 34 at leastpartially supports a ball screw mechanism 38. A trigger 174 foroperating the crimping tool 10 is provided on the handle portion 34.

With reference to FIG. 3, the crimping tool 10 also includes an innerhousing 42 disposed at least partially within the handle portion 34 ofthe outer housing 14. In the illustrated embodiment, the inner housing42 includes an exposed portion 46 that extends beyond a front end of thehandle portion 34. The exposed portion 46 of the inner housing 42defines a clevis 50 to which a working assembly 54 (e.g., pair of jaws58) is pivotably and detachably coupled. As is described in more detailbelow, the drive unit 30 is operatively coupled to the jaws 58 toperform a crimping operation on a workpiece (e.g., a PEX fitting, notshown).

Referring to FIGS. 3-5, the drive unit 30 includes a motor 62, atransmission 66, and an output shaft 70. In the illustrated embodimentof the crimping tool 10, the motor 62 is a brushless DC electric motor62 capable of producing a rotational output through a drive shaft 74which, in turn, provides a rotational input to the transmission 66. Inthe illustrated embodiment, the transmission 66 is configured as aplanetary transmission 66 having three planetary stages 66 a, 66 b, 66c, though any number of planetary stages may alternatively be used. Theoutput shaft 70 is coupled for co-rotation with a carrier 78 (FIG. 4) inthe third planetary stage 66 a of the transmission 66 to thereby receivethe torque output of the transmission 66. As shown in FIGS. 4 and 5, theoutput shaft 70 is configured as a hollow tube having axially extendingsplines 82 on an inner surface 86 thereof, and is disposed at leastpartially within the handle portion 34 of the outer housing 14. A distalend of the output shaft 70 is rotatably supported within the handleportion 34 by a bearing 90 (e.g., a sleeve bearing or bushing; FIG. 4).

The transmission 66 further includes a gear case or transmission housing94 separated from the inner housing 42, but rotationally constrainedwith the inner housing 42 by the outer housing 14 (FIG. 3). In otherwords, the outer housing 14 is not merely an enclosure, but rather astructural or force-bearing member of the crimping tool 10 that exerts areaction torque on the inner housing 42 during a crimping operation.Without such a reaction torque applied to the inner housing 42, theinner housing 42 and jaws 58 would co-rotate with the ball screwmechanism 38 (FIG. 4) in response to rotation of the output shaft 70.Accordingly, the handle portion 34 of the outer housing 14 is subject tostress during operation of the crimping tool 10, which would not be thecase if the inner housing 42 were connected directly to the transmissionhousing 94.

With reference to FIG. 4, the ball screw mechanism 38 includes anextensible member or screw 98 and a nut 102 that is fixed to the innerhousing 42. The screw 98 includes a threaded outer surface 106 withwhich the nut 102 is engageable. A plurality of balls 122 are capturedbetween the threaded outer surface 106 and the nut 102 to reducefriction between the screw 98 and the nut 102 and to inhibit backlash.The ball screw mechanism 38 further includes a splined nut 110 affixedto a proximal end 114 (i.e. the end closest to the drive unit 30) of thescrew 98. Best illustrated in FIG. 7, the splined nut 110 includes aplurality of splines 112 disposed circumferentially about the splinednut 110, with one or more spaces 116 formed by the absence of at leastone spline 112. In the illustrated embodiment, the spaces 116 aredisposed approximately 180° apart and are formed by the absence of twosplines 112. However, other configurations (e.g., the number of splines112 absent from space 116, the number of spaces 116, the angular spacingof spaces 116, etc.) are possible. The splines 112 of the splined nut110 engage the splines 82 (FIG. 5) on the inner surface 86 of the outputshaft 70, thereby causing the splined nut 110 to co-rotate with theoutput shaft 70 while being axially movable relative to the output shaft70. The spaces 116 facilitate the passage of air past the nut 110 toreduce pressure gradients within the ball screw mechanism 38 on opposingsides of the splined nut 110 as the splined nut 110 is axiallydisplaced.

With reference to FIGS. 4 and 5, the crimping tool 10 also includes aroller carriage 126 coupled to a distal end 130 (i.e. the end farthestfrom the drive unit 30) of the screw 98. The roller carriage 126includes a mount 134, a carriage 138 upon which two rollers 142 aresupported, and a thrust bearing assembly 146 (FIG. 4) between the mount134 and the carriage 138. The thrust bearing assembly 146 permits thescrew 98 to rotate freely relative to the carriage 126, therebypermitting the inner housing 42 to restrict rotational movement of thecarriage 126 while permitting axial displacement. Each of the rollers142 is rotatable about an axis 144 oriented substantially transverse toa rotational axis 148 of the output shaft 70 and screw 98 (FIG. 4). Inthe illustrated embodiment, the rotational axes 144 of the respectiverollers 142 are positioned on opposite sides of the rotational axis 148of the output shaft 70 and screw 98.

With reference to FIGS. 3 and 4, the jaws 58 are pivotably coupled to abracket 150 about respective parallel axes 156 a, 156 b by pins 152(FIG. 3). Each of the jaws 58 includes a distal crimping portion 154 anda proximal arm 158 located on opposite sides of the pin (FIG. 4). Eachof the arms 158 includes a cam surface 162 that is engageable with therespective rollers 142. The jaws 58 are biased toward a closedconfiguration by a biasing member 166, such as a leaf spring. To latchthe jaws 58 to a workpiece in preparation for a crimping operation, auser may press an outer surface 170 of each of the arms 158, therebyplacing the jaws 58 in an open configuration in which the crimpingportions 154 of the jaws 58 are spaced from each other an amountsufficient to position the workpiece between the crimping portions 154.When the user releases the arms 158, the jaws 58 are returned toward theclosed configuration by the biasing member 166 until the crimpingportions of the jaws 58 engage the workpiece.

Optionally, the working assembly 54, including the jaws 58, may bedetachably coupled to the clevis 50 of the inner housing 42 by anysuitable manner (e.g., pin coupling, ball detent, etc.). Thisconfiguration allows multiple working assemblies to be attached to thetool, each having a different operation (e.g., crimping, cutting,expanding, etc.). The detachable coupling also facilitates thereplacement of worn or damaged jaws 58.

FIGS. 8-11 illustrate an alternate embodiment of the working assembly54, illustrated as a pair of jaws 258, which may be used in conjunctionwith the crimping tool 10. The jaws 258 are substantially similar to thejaws 58, with like features being shown with the same reference numeralsplus “100.” This description will focus on the differences between jaws58 and jaws 258.

FIG. 9 illustrates the jaws 258 with the bracket 250 removed to expose apivot pin 264 about which the jaws 258 pivot, and the biasing member 266(e.g., a leaf spring). With reference to FIGS. 10 and 11, the pivot pin264 includes an outer diameter 270, which interfaces with the jaws 258to reduce jaw mismatch and improve crimp alignment, and acircumferential groove 268 sized and shaped to receive the biasingmember 266. The circumferential groove 268 is configured to maintainproper alignment of the leaf spring relative to the pivot pin 264 andthe jaws 258.

With reference to FIG. 6, the crimping tool further includes a controlsystem 200 including a first sensor 204 disposed on the inner housing 42for detecting the position of the roller carriage 126, a second sensor208 associated with the motor 62, and a controller 212. As is describedin greater detail below, the first sensor 204 is configured to detectthe proximity of the roller carriage 126 relative to the inner housing42 and output a corresponding first signal, while the second sensor 208is configured to count the revolutions of the motor 62 and output acorresponding second signal. The controller 212 is capable ofinterpreting the first and second signals and operating the motor 62based on the received signals.

With reference to FIGS. 3 and 5, the first sensor 204 is configured as aHall-effect sensor mounted on a printed circuit board 224 coupled to anouter periphery of the inner housing 42. The roller carriage 126includes a magnet (not shown) fixed to the carriage 138 so as to beaxially displaceable with the carriage 138. The first sensor 204 detectsthe proximity of the magnet, and therefore the roller carriage 126, bydetecting and measuring the magnetic field emanated by the magnet. Thefirst sensor 204 is positioned along the length of the inner housing 42to detect a “zero” or home position of the roller carriage 126 relativeto the inner housing 42 (i.e., a position in which the roller carriage126 is retracted so to not interfere with opening of the jaws 58 priorto a crimping operation).

The second sensor 208 (FIG. 6) is configured as a plurality ofHall-effect sensors (e.g., three Hall-effect sensors) and isincorporated within the motor 62 for counting the number of revolutionsof the drive shaft 74 as it rotates in one direction (i.e., coincidingwith extension of the screw 98). The second sensor 208 may also countthe number of revolutions of the drive shaft 74 in the oppositedirection (i.e., coinciding with retraction of the screw 98).

In some embodiments, the control system 200 may use a current sensor 232to generate a third signal used by the controller 212. The currentsensor 232 may measure the electrical current being used by the motor62, which may drastically increase if the jaws 58 are impeded, forexample, by an obstruction or a material that is too hard to crimp. Inthis case, the controller 212 may alter operation of the motor 62 (e.g.,stopping or reversing it) to prevent damage to the tool 10 in responseto the controller 212 detecting an electrical current greater than apredetermined value.

In operation of the tool 10, a user depresses the trigger 174 to providepower from the battery 22 to the motor 62, which rotates the drive shaft74 (FIG. 4). The drive shaft 74 in turn rotates the transmission 66,which drives the output shaft 70. When the output shaft 70 rotates, thescrew 98 also rotates due to the engagement between the splines 82 onthe output shaft 70 and the splines 112 on the splined nut 110. As thescrew 98 rotates relative to the nut 102, the threaded engagement causesthe screw 98 to be axially displaced relative to the nut 102 and theinner housing 42. On the proximal end 114 of the screw 98, the splinednut 110 is allowed to slide axially along the splines 82 on the innersurface 86 of the output shaft 70. On the distal end 130 of the screw98, relative rotation between the screw 98 and the roller carriage 126is permitted by the thrust bearing assembly 146. Movement of the rollercarriage 126, in turn, is confined to axial displacement along the innerhousing 42. As the screw 98 and roller carriage 126 are axiallydisplaced, the rollers 142 engage the respective cam surfaces 162 of thejaws 58 and apply a force normal to the cam surface 162 that acts topivot the jaws 58 about their respective pins 152, thereby closing thejaws 58 to perform a crimping operation on the workpiece.

During a crimping operation, rotation of the output shaft 70 and screw98 exerts a torque on the nut 102, which is ultimately transmitted tothe inner housing 42. However, in response, the handle portion 34 exertsa reaction torque on the inner housing 42 to prevent the inner housing42 from rotating relative to the handle portion 34. Accordingly, thehandle portion 34 of the outer housing 14 is subject to stress andfunctions as a structural or force-bearing member during the crimpingoperation, as opposed to functioning merely as an enclosure.

Referring also to FIG. 6, during operation, the controller 212 sets amotor revolution counter to zero if the first sensor 204 detects theroller carriage 126 in the home position. If the roller carriage 126 isnot in the home position, the motor 62 is operated in a reversedirection until the home position of the roller carriage 126 is detected(i.e., in response to the first sensor 204 outputting the first signal).If the roller carriage 126 is in the home position when the trigger 174is actuated, the motor 62 drives the ball screw mechanism 38 to impartan axial displacement to the roller carriage 126 to close the jaws 58and perform a crimping operation. During this process, the controller212 (using the second signal provided by the second sensor 208) operatesthe motor 62 to turn at least a minimum predetermined number ofrevolutions while also monitoring electrical current used by the motor62 (using the third signal provided by the current sensor 232) toperform a crimping operation. Once this minimum number of revolutions isreached and the amount of current drawn by the motor 62 reaches apredetermined value, the controller 212 reverses the motor 62 at a highspeed to retract the roller carriage 126 and remove the rollers 142 fromengagement with the respective cam surfaces 162 of the jaws 58. Thecontroller 212 continues to operate the motor 62 in a reverse directionuntil the motor revolution counter returns to zero and the home positionof the roller carriage 126 is detected (using the first signal providedby the first sensor 204). Thereafter, the controller 212 deactivates themotor 62, thus readying the crimping tool 10 for a subsequent crimpingoperation upon actuation of the trigger 174.

Furthermore, the controller 212 is also operable to detect a foreignobject overloading the jaws 58. In such operation, the trigger 174 isactuated, and the motor 62 drives the ball screw mechanism 38 to impartan axial displacement to the roller carriage 126 to close the jaws 58and attempt to perform a crimping operation. During this process, thecontroller 212 monitors the current being drawn by the motor 62 (usingthe third signal provided by the current sensor 232) and counts thenumber of revolutions of the motor (using the second signal provided bythe second sensor 208). If the controller 212 detects the current beingdrawn by the motor 62 is greater than a predetermined value for aspecified number of motor revolutions (e.g., the motor is highly loadedtoo early in the crimping operation), the controller 212 reverses themotor 62. The controller 212 continues to operate the motor 62 in areverse direction until the motor 62 revolution count returns to zeroand the home position of the roller carriage 126 is detected (using thefirst signal provided by the first sensor 204).

In some embodiments, the controller 212 may employ a similar operationalmethod when the working assembly 54 is detached from the tool 10.Specifically, upon actuation of the trigger 174, the motor 62 drives theball screw mechanism 38 to impart an axial displacement to the rollercarriage 126. During this process, the controller 212 monitors thecurrent being drawn by the motor 62 (using the third signal provided bythe current sensor 232) and counts the number of revolutions of themotor (using the second signal provided by the second sensor 208). Ifthe controller 212 detects that the motor 62 has reached a predeterminednumber of revolutions and the current being drawn has not changedsignificantly (as a result of no reaction forces being imparted to themissing working assembly 54), the controller 212 reverses the motor 62until the motor revolution counter returns to zero and the home positionof the roller carriage 126 is detected (using the first signal providedby the first sensor 204). The controller 212 may also be operable toalert the user that a working assembly 54 is not coupled to the tool 10.

The power tool 10, as described above, is advantageous in that itprovides an inline, compact drive configuration while limiting thenumber of parts necessary to maintain strength and stability. Inparticular, using the handle portion 34 of the outer housing 14 as astructural or force-bearing member eliminates the need and attendantcost of additional material for directly connecting the inner housing 42and the transmission housing 94. The tool also provides an electroniccontrol system 200 to count motor revolutions, detect a home position ofthe roller carriage 126, and/or measure motor current to enhance thequality and repeatability of tool functions (e.g., crimping).

Various features of the invention are set forth in the following claims.

What is claimed is:
 1. A power tool comprising: an outer housingincluding a drive unit support portion and a handle portion; an innerhousing positioned at least partially within the outer housing; a driveunit positioned in the drive unit support portion and including anoutput member; a power screw mechanism including a nut fixed relative tothe outer housing, and a screw coupled for co-rotation with the outputmember and axially movable relative to the output member, wherein thescrew is in threaded engagement with the nut such that the screw movesaxially in response to rotation of the screw relative to the nut; and aworking assembly coupled to the inner housing for movement in responseto axial movement of the screw.
 2. The power tool of claim 1, furthercomprising a roller carriage coupled to the screw for axial movementtherewith between a retracted position and an extended position, whereinthe working assembly includes a plurality of j aws engageable with theroller carriage such that movement of the roller carriage from theretracted position toward the extended position moves the jaws toward aclosed position.
 3. The power tool of claim 1, further comprising asplined member fixed to the screw, the splined member including aplurality of external splines, wherein the output member includes aplurality of internal splines meshed with the external splines of thesplined member.
 4. The power tool of claim 3, wherein the plurality ofexternal splines includes a first spline, a second spline adjacent thefirst spline, and a third spline adjacent the second spline, wherein thesecond spline is circumferentially spaced from the first spline by afirst distance, wherein the third spline is circumferentially spacedfrom the second spline by a second distance, and wherein the seconddistance is greater than the first distance to define a gap in theplurality of splines between the second spline and the third spline. 5.The power tool of claim 1, wherein the handle portion exerts a reactiontorque on the inner housing in response to the relative rotation betweenthe nut and the screw to prevent the inner housing from rotatingrelative to the outer housing.
 6. The power tool of claim 1, wherein thescrew is at least partially positioned within the handle portion.
 7. Thepower tool of claim 1, wherein the output member is at least partiallypositioned within the handle portion.
 8. The power tool of claim 1,wherein the output member includes a hollow tube within which the screwis at least partially received.
 9. The power tool of claim 1, whereinthe drive unit includes a motor and a transmission coupled to the motorfor receiving torque therefrom, and wherein the output member isdrivably coupled to an output of the transmission.
 10. The power tool ofclaim 1, wherein the inner housing is spaced apart from the drivehousing support portion.
 11. The power tool of claim 10, wherein theouter housing includes a battery support portion, and wherein the driveunit support portion is adjacent each of the handle portion and thebattery support portion.
 12. The power tool of claim 1, wherein theworking assembly includes first and second jaws pivotally coupled to theinner housing, a pin positioned between the first and second jaws, and abiasing member coupled to the pin, the biasing member configured to biasthe first and second jaws toward a closed position.
 13. The power toolof claim 12, wherein the pin includes a circumferential groove in whichthe biasing member is at least partially received.
 14. A power toolcomprising: an outer housing including a drive unit support portion anda handle portion; an inner housing positioned at least partially withinthe outer housing; a drive unit positioned in the drive unit supportportion and including an output member; a roller carriage movablebetween a retracted position and an extended position in response torotation of the output member; and a working assembly movable inresponse to contact with the roller carriage, the working assemblyincluding first and second jaws pivotally coupled to the inner housing,a pin positioned between the first and second jaws and including acircumferential groove, and a biasing member at least partially receivedwithin the circumferential groove, the biasing member configured to biasthe first and second jaws toward a closed position.
 15. The power toolof claim 14, wherein the inner housing is spaced apart from the driveunit support portion.
 16. The power tool of claim 15, further comprisinga screw coupled for co-rotation with the output member, wherein thescrew is at least partially positioned within the handle portion.
 17. Apower tool comprising: an outer housing including a drive unit supportportion and a handle portion; an inner housing positioned at leastpartially within the outer housing; a drive unit positioned in the driveunit support portion and including an output member having a pluralityof internal splines; a power screw mechanism including a nut fixedrelative to the outer housing, a screw in threaded engagement with thenut such that the screw moves axially in response to rotation of thescrew relative to the nut, and a splined member fixed to the screw, thesplined member including a plurality of external splines meshed with theinternal splines of the output member; and a working assembly coupled tothe inner housing for movement in response to axial movement of thescrew.
 18. The power tool of claim 17, wherein the plurality of externalsplines includes a first spline, a second spline adjacent the firstspline, and a third spline adjacent the second spline, wherein thesecond spline is circumferentially spaced from the first spline by afirst distance, wherein the third spline is circumferentially spacedfrom the second spline by a second distance, and wherein the seconddistance is greater than the first distance to define a gap in theplurality of splines between the second spline and the third spline. 19.The power tool of claim 17, wherein the output member is at leastpartially positioned within the handle portion.
 20. The power tool ofclaim 19, wherein the output member includes a hollow tube within whichthe screw is at least partially received.